Heart sounds are generally associated with the mechanical vibrations from the activity of a subject's heart and the flow of blood through the heart. Because of this association, heart sounds typically recur with each cardiac cycle of a heart, and are typically separated and classified into one of four types according to the activity associated with the vibration: S1, S2, S3, and S4. S1 (commonly referred to in the art as “the first heart sound”) is typically associated with the vibrational sound made by the heart during tensing of the mitral valve. S2 (commonly referred to in the art as “the second heart sound”) is typically associated with the beginning of diastole. S3 (commonly referred to in the art as “the third heart sound”) and S4 (commonly referred to in the art as “the fourth heart sound”) are typically associated with the filling pressures of the left ventricle during diastole. Generally, heart sounds can be used as indications of proper or improper functioning of a subject's heart.